The 2012 ASHS Annual Conference

In ethylene-sensitive plants, such as carnation, ethylene perception is considered an indispensable requirement to initiate and perpetuate the ethylene-mediated senescence program. Ethylene binding antagonists, such as 1-methylcyclopropene (1-MCP) compete for ethylene binding and block senescence. Despite its antagonistic propensity, plants treated with 1-MCP often recover sensitivity to ethylene post-treatment. We used carnations (Dianthus caryophyllus L. ‘Glacier’) to determine the relationship between petal inrolling patterns and the expression of genes involved in ethylene biosynthesis and ethylene signaling after treatment of petals with ethylene and 1-MCP. Petal inrolling began after 10 h of ethylene treatment and petals were completely inrolled within 1 h from the first visible sign of inrolling. In these petals, ethylene biosynthetic genes DcACS1 and DcACO1 increased greatly, but receptor and response genes DcETR1 and DcCTR1 were initially high and decreased gradually. When petals were treated with 100 nL·L^-1 1-MCP and then treated daily with 10 μL·L^-1 ethylene, we monitored the gene expression changes after treatment with 1-MCP one, two, or multiple times at 3 d intervals. This study revealed that the mRNA levels of DcETR1 and DcCTR1 gradually decrease during ethylene treatment, but increase at certain times during flower development, and that this increase occurs concomitant with onset of petal inrolling. The results suggest that after treatment with 1-MCP, ethylene receptors genes are transcribed during flower development. The newly generated receptor proteins are likely to be bound with ethylene, leading to the observed recovery of ethylene-sensitivity in the petals post-treatment of 1-MCP. The current study also suggests that ethylene binding to new receptors is prevented by successive treatment of 1-MCP prior to regaining of ethylene-sensitivity, resulting in repression of petal senescence and inrolling.